Peat (/piːt/), awso known as turf (/tɜːrf/), is an accumuwation of partiawwy decayedvegetation or organic matter. It is uniqwe to naturaw areas cawwed peatwands, bogs, mires, moors, or muskegs.[1][2] The peatwand ecosystem is de most efficient carbon sink on de pwanet,[2] because peatwand pwants capture CO2 naturawwy reweased from de peat, maintaining an eqwiwibrium. In naturaw peatwands, de "annuaw rate of biomass production is greater dan de rate of decomposition", but it takes "dousands of years for peatwands to devewop de deposits of 1.5 to 2.3 m [4.9 to 7.5 ft], which is de average depf of de boreaw [nordern] peatwands".[2]Sphagnum moss, awso cawwed peat moss, is one of de most common components in peat, awdough many oder pwants can contribute. The biowogicaw features of Sphagnum mosses act to create a habitat aiding peat formation, a phenomenon termed 'habitat manipuwation'.[3] Soiws consisting primariwy of peat are known as histosows. Peat forms in wetwand conditions, where fwooding obstructs de fwow of oxygen from de atmosphere, swowing de rate of decomposition, uh-hah-hah-hah.[4]

Peatwands, particuwarwy bogs, are de primary source of peat,[5]
awdough wess-common wetwands incwuding fens, pocosins, and peat swamp forests awso deposit peat. Landscapes covered in peat are home to specific kinds of pwants incwuding Sphagnum moss, ericaceous shrubs, and sedges (see bog for more information on dis aspect of peat). Because organic matter accumuwates over dousands of years, peat deposits provide records of past vegetation and cwimate by preserving pwant remains, such as powwen, uh-hah-hah-hah. This awwows humans to reconstruct past environments and study changes in human wand use.[6]

Peat is harvested as an important source of fuew in certain parts of de worwd. By vowume, dere are about 4 triwwion cubic metres (5.2 triwwion cubic yards) of peat in de worwd, covering a totaw of around 2% of de gwobaw wand area (about 3 miwwion sqware kiwometres or 1.2 miwwion sqware miwes), containing about 8 biwwion terajouwes of energy.[7] Over time, de formation of peat is often de first step in de geowogicaw formation of oder fossiw fuews such as coaw, particuwarwy wow-grade coaw such as wignite.[8]

Peat forms when pwant materiaw does not fuwwy decay in acidic and anaerobic conditions. It is composed mainwy of wetwand vegetation: principawwy bog pwants incwuding mosses, sedges, and shrubs. As it accumuwates, de peat howds water. This swowwy creates wetter conditions dat awwow de area of wetwand to expand. Peatwand features can incwude ponds, ridges, and raised bogs.[5]

Most modern peat bogs formed 12,000 years ago in high watitudes after de gwaciers retreated at de end of de wast ice age.[16] Peat usuawwy accumuwates swowwy at de rate of about a miwwimetre per year.[9]

Peat materiaw is eider fibric, hemic, or sapric. Fibric peats are de weast decomposed and consist of intact fibre. Hemic peats are partiawwy decomposed and sapric are de most decomposed.[17]

Phragmites peat are composed of reed grass, Phragmites austrawis, and oder grasses. It is denser dan many oder types of peat.

Engineers may describe a soiw as peat which has a rewativewy high percentage of organic materiaw. This soiw is probwematic because it exhibits poor consowidation properties – it cannot be easiwy compacted to serve as a stabwe foundation to support woads, such as roads or buiwdings.

...de most widespread of aww wetwand types in de worwd, representing 50 to 70% of gwobaw wetwands. They cover over 4 miwwion sqware kiwometres [1.5 miwwion sqware miwes] or 3% of de wand and freshwater surface of de pwanet. In dese ecosystems are found one dird of de worwd’s soiw carbon and 10% of gwobaw freshwater resources. These ecosystems are characterized by de uniqwe abiwity to accumuwate and store dead organic matter from Sphagnum and many oder non-moss species, as peat, under conditions of awmost permanent water saturation, uh-hah-hah-hah. Peatwands are adapted to de extreme conditions of high water and wow oxygen content, of toxic ewements and wow avaiwabiwity of pwant nutrients. Their water chemistry varies from awkawine to acidic. Peatwands occur on aww continents, from de tropicaw to boreaw and Arctic zones from sea wevew to high awpine conditions.

— Joosten and Cwarke 2002

Peatwands are areas of wand wif naturawwy formed wayers of peat. They can be found in at weast 175 countries and cover around 4 miwwion sqware kiwometres (1.5 miwwion sqware miwes); dat is 3% of de worwd’s wand area. In Europe, peatwands extend to about 515,000 km2 (199,000 sq mi).[18] About 60% of de worwd's wetwands are made of peat.

Peat deposits are found in many pwaces around de worwd, incwuding nordern Europe and Norf America. The Norf American peat deposits are principawwy found in Canada and de Nordern United States. Some of de worwd's wargest peatwands incwude de West Siberian Lowwand, de Hudson Bay Lowwands, and de Mackenzie River Vawwey.[19]
There is wess peat in de Soudern Hemisphere, in part because dere is wess wand. That said, de vast Magewwanic Moorwand in Souf America (Soudern Patagonia/Tierra dew Fuego) is an extensive peat-dominated wandscape.[19] Peat can be found in New Zeawand, Kerguewen, de Fawkwand Iswands, and Indonesia (Kawimantan [Sungai Putri, Danau Siawan, Sungai Towak], Rasau Jaya [West Kawimantan], and Sumatra). Indonesia has more tropicaw peatwands and mangrove forests dan any oder nation on earf, but Indonesia is wosing wetwands by 100,000 hectares (250,000 acres) per year.[20]

About 7% of aww peatwands have been expwoited for agricuwture and forestry.[21] Under proper conditions, peat wiww turn into wignite coaw over geowogic periods of time.

Under pressure, water is forced out of peat, which is soft and easiwy compressed, and once dry can be used as fuew. In many countries, incwuding Irewand and Scotwand, peat has traditionawwy been used for cooking and domestic heating, and peat is stacked to dry in ruraw areas. It remains harvested on an industriaw scawe for dis purpose in countries such as Irewand and Finwand. Its insuwating properties make it usefuw in industry.

Awdough humans have many uses for peat, it presents severe probwems at times. Wet or dry, it can be a major fire hazard. Peat fires may burn for great wengds of time, or smouwder underground and reignite after winter if an oxygen source is present. Because dey are easiwy compressed under minimaw weight, peat deposits pose major difficuwties to buiwders of structures, roads, and raiwways. When de West Highwand raiwway wine was buiwt across Rannoch Moor in western Scotwand, its buiwders had to fwoat de tracks on a muwti-dousand-ton mattress of tree roots, brushwood, earf and ash.

In de Bronze and Iron Ages, peopwe used peat bogs for rituaws to nature gods and spirits.[citation needed] Bodies of de victims of such sacrifices have been found in various pwaces in Scotwand, Engwand, Irewand, and especiawwy nordern Germany and Denmark. They are awmost perfectwy preserved by de tanning properties of de acidic water (see Towwund Man for one of de most famous exampwes of a bog body). Peat wetwands awso used to have a degree of metawwurgicaw importance, being during de Dark Ages de primary source of bog iron dat was used to create swords and armour for Vikings. Many peat swamps awong de coast of Mawaysia serve as a naturaw means of fwood mitigation, wif any overfwow being absorbed by de peat, provided forests are stiww present to prevent peat fires.

The cwimate, geography, and environment of Finwand favours bog and peat bog formation, uh-hah-hah-hah. Thus, peat is avaiwabwe in considerabwe qwantities. This abundant resource (often mixed wif wood at an average of 2.6%) is burned to produce heat and ewectricity. Peat provides around 6.2% of Finwand's annuaw energy production, second onwy to Irewand.[22] The contribution of peat to greenhouse gas emissions of Finwand can exceed 10 miwwion metric tonnes of carbon dioxide per year – eqwaw to de totaw emissions of aww passenger-car traffic in Finwand.

Finwand cwassifies peat as a swowwy renewing biomass fuew.[23] Peat producers in Finwand often cwaim dat peat is a speciaw form of biofuew because of de rewativewy fast retake rate of reweased CO2 if de bog is not forested for de fowwowing 100 years. Awso, agricuwturaw and forestry-drained peat bogs activewy rewease more CO2 annuawwy dan is reweased in peat energy production in Finwand. The average regrowf rate of a singwe peat bog, however, is indeed swow, from 1,000 up to 5,000 years. Furdermore, it is a common practice to forest used peat bogs instead of giving dem a chance to renew. This weads to wower wevews of CO2 storage dan de originaw peat bog.

At 106 g CO2/MJ,[24] de carbon dioxide emissions of peat are higher dan dose of coaw (at 94.6 g CO2/MJ) and naturaw gas (at 56.1). According to one study, increasing de average amount of wood in de fuew mixture from de current 2.6% to 12.5% wouwd take de emissions down to 93 g CO2/MJ. That said, wittwe effort is being made to achieve dis.[25]

The Internationaw Mire Conservation Group (IMCG) in 2006 urged de wocaw and nationaw governments of Finwand to protect and conserve de remaining pristine peatwand ecosystems. This incwudes de cessation of drainage and peat extraction in intact mire sites and de abandoning of current and pwanned groundwater extraction dat may affect dese sites. A proposaw for a Finnish peatwand management strategy was presented to de government in 2011, after a wengdy consuwtation phase.[26]

Industriaw-miwwed peat production in a section of de Bog of Awwen in de Irish Midwands: The 'turf' in de foreground is machine-produced for domestic use.

In Irewand, warge-scawe domestic and industriaw peat usage is widespread. In de Repubwic of Irewand, a state-owned company cawwed Bord na Móna is responsibwe for managing peat extraction, uh-hah-hah-hah. It processes de extracted peat into miwwed peat which is used in power stations and sewws processed peat fuew in de form of peat briqwettes which are used for domestic heating. These are obwong bars of densewy compressed, dried, and shredded peat. Peat moss is a manufactured product for use in garden cuwtivation, uh-hah-hah-hah. Turf (dried out peat sods) is awso commonwy used in ruraw areas.

In de 1960s, warger sections of swamps and bogs in Western Russia were drained for agricuwturaw and mining purposes.[27] Pwans are underway to increase peat output and increase peat's contribution to Russian energy generation, uh-hah-hah-hah.[28] There is concern about de environmentaw impact as peat fiewds are fwammabwe, drainage degrades ecosystems, and burning of peat reweases carbon dioxide.[28] Due to 2010 forest and peat fires, de Russian government is under heavy pressure to finance re-fwooding of de previouswy drained bogs around Moscow. The initiaw costs for de programme are estimated to be about 20 to 25 biwwion rubwes; dat is cwose to 500 miwwion euros (540 miwwion USD).

2500 years BP de area now named de Nederwands was wargewy covered wif peat. Drainage, causing compaction and oxidation and excavation have reduced peatwands to about 3,356 km2 (1,296 sq mi) [31] or 10% of de wand area, mostwy used as meadows. Drainage and excavation have wowered de surface of de peatwands. In de west of de country dikes and miwws were buiwt, creating powders so dat dwewwing and economic activities couwd continue bewow sea wevew. The first powder was in de 11f century, and de wast in 1968. Harvesting of peat couwd continue in suitabwe wocations as de wower peat wayers bewow current sea wevew became exposed. They were deposited before de rise of de sea wevew in de Howocene. As a resuwt approximate 26% of its area [32] and 21% of its popuwation [33] of de Nederwands are presentwy bewow sea wevew. The deepest point is in de Zuidpwaspowder, 6.76 m (22.2 ft) bewow average sea wevew.

The extraction of peat from de Somerset Levews began during de Roman times and has been carried out since de Levews were first drained.[34] On Dartmoor, dere were severaw commerciaw distiwwation pwants formed and run by de British Patent Naphda Company in 1844. These produced naphda on a commerciaw scawe from de high-qwawity wocaw peat.[35]

Some Scotch whisky distiwweries, such as dose on Isway, use peat fires to dry mawted barwey. The drying process takes about 30 hours. This gives de whiskies a distinctive smoky fwavour, often cawwed "peatiness".[38]
The peatiness, or degree of peat fwavour, of a whisky, is cawcuwated in ppm of phenow. Normaw Highwand whiskies have a peat wevew of up to 30 ppm, and de whiskies on Isway usuawwy have up to 50 ppm. In rare types wike de Octomore,[39] de whisky can have more dan 100 ppm of phenow. Scotch Awes can awso use peat roasted mawt, imparting a simiwar smoked fwavor.

In Sweden, farmers use dried peat to absorb excrement from cattwe dat are wintered indoors. The most important property of peat is retaining moisture in container soiw when it is dry whiwe preventing de excess of water from kiwwing roots when it is wet. Peat can store nutrients awdough it is not fertiwe itsewf – it is powyewectrowytic wif a high ion-exchange capacity due to its oxidized wignin, uh-hah-hah-hah. Peat is discouraged as a soiw amendment by de Royaw Botanic Gardens, Kew, Engwand, since 2003.[40] Whiwe bark-based peat-free potting soiw mixes are on de rise, particuwarwy in de U.K., peat remains an important raw materiaw for horticuwture in Canada, as weww as parts of de United States. However, it is recommended to treat peat dermawwy, e.g., drough soiw steaming in order to kiww pests and reactivate nutrients.

Peat is sometimes used in freshwater aqwaria. It is seen most commonwy in soft water or bwackwater river systems such as dose mimicking de Amazon River basin, uh-hah-hah-hah. In addition to being soft in texture and derefore suitabwe for demersaw (bottom-dwewwing) species such as Corydoras catfish, peat is reported to have a number of oder beneficiaw functions in freshwater aqwaria. It softens water by acting as an ion exchanger; it awso contains substances dat are beneficiaw for pwants, and for de reproductive heawf of fishes. Peat can prevent awgae growf and kiww microorganisms. Peat often stains de water yewwow or brown due to de weaching of tannins.[41]

Peat is widewy used in bawneoderapy (de use of bading to treat disease). Many traditionaw spa treatments incwude peat as part of pewoids. Such heawf treatments have an enduring tradition in European countries incwuding Powand, de Czech Repubwic, Germany, and Austria. Some of dese owd spas date back to de 18f century and are stiww active today. The most common types of peat appwication in bawneoderapy are peat muds, pouwtices, and suspension bads.[42]

Audors Rydin and Jegwum in Biowogy of Habitats described de concept of peat archives, a phrase coined by infwuentiaw peatwand scientist Harry Godwin in 1981.[43][44][45]

In a peat profiwe dere is a fossiwized record of changes over time in de vegetation, powwen, spores, animaws (from microscopic to de giant ewk), and archaeowogicaw remains dat have been deposited in pwace, as weww as powwen, spores and particwes brought in by wind and weader. These remains are cowwectivewy termed de peat archives.

— Rydin, 2013

In Quaternary Pawaeoecowogy, first pubwished in 1980, Birks and Birks described how paweoecowogicaw studies "of peat can be used to reveaw what pwant communities were present (wocawwy and regionawwy), what time period each community occupied, how environmentaw conditions changed, and how de environment affected de ecosystem in dat time and pwace."[44][46]

Scientists continue to compare modern mercury (Hg) accumuwation rates in bogs wif historicaw naturaw-archives records in peat bogs and wake sediments to estimate de potentiaw human impacts on de biogeochemicaw cycwe of mercury, for exampwe.[47] Over de years, different dating modews and technowogies for measuring date sediments and peat profiwes accumuwated over de wast 100–150 years, have been used, incwuding de widewy used verticaw distribution of 210Pb, de inductivewy coupwed pwasma mass spectrometry (ICP-SMS),[48] and more recentwy de initiaw penetration (IP).[49]

Peat "hags" are a form of erosion dat occurs at de sides of guwwies dat cut into de peat or, sometimes, in isowation, uh-hah-hah-hah.[50] Hags may resuwt when fwowing water cuts downwards into de peat and when fire or overgrazing exposes de peat surface. Once de peat is exposed in dese ways, it is prone to furder erosion by wind, water, and wivestock. The resuwt is overhanging vegetation and peat. Hags are too steep and unstabwe for vegetation to estabwish itsewf, so dey continue to erode unwess restorative action is taken, uh-hah-hah-hah.[50]

Increase, and change rewative to previous year, of de atmospheric concentration of carbon dioxide.

The distinctive ecowogicaw conditions of peat wetwands provide a habitat for distinctive fauna and fwora. For exampwe, whooping cranes nest in Norf American peatwands, whiwe Siberian cranes nest in de West Siberian peatwand. Such habitats awso have many species of wiwd orchids and carnivorous pwants. It takes centuries for a peat bog to recover from disturbance. (For more on biowogicaw communities, see wetwand, bog or fen.)

The worwd's wargest peat bog is wocated in Western Siberia. It is de size of France and Germany combined. Recent studies show dat it is dawing for de first time in 11,000 years. As de permafrost mewts, it couwd rewease biwwions of tonnes of medane gas into de atmosphere. The worwd's peatwands are dought to contain 180 to 455 biwwion metric tonnes of seqwestered carbon, and dey rewease into de atmosphere 20 to 45 miwwion metric tons of medane annuawwy. The peatwands' contribution to wong-term fwuctuations in dese atmospheric gases has been a matter of considerabwe debate.[51]

One of de characteristics for peat is de bioaccumuwations of metaws often concentrated in de peat. Accumuwated mercury is of significant environmentaw concern, uh-hah-hah-hah.[52]

Large areas of organic wetwand (peat) soiws are currentwy drained for agricuwture, forestry, and peat extraction, uh-hah-hah-hah. This process is taking pwace aww over de worwd. This not onwy destroys de habitat of many species but awso heaviwy fuews cwimate change.[citation needed] As a resuwt of peat drainage, de organic carbon – which buiwt over dousands of years and is normawwy underwater – is suddenwy exposed to de air. It decomposes and turns into carbon dioxide (CO2), which is reweased into de atmosphere.[53] The gwobaw CO2 emissions from drained peatwands have increased from 1,058 Mton in 1990 to 1,298 Mton in 2008 (a 20% increase). This increase has particuwarwy taken pwace in devewoping countries, of which Indonesia, China, Mawaysia, and Papua New Guinea are de fastest-growing top emitters. This estimate excwudes emissions from peat fires (conservative estimates amount to at weast 4,000 Mton/CO2-eq./yr for souf-east Asia). Wif 174 Mton/CO2-eq./yr de EU is after Indonesia (500 Mton) and before Russia (161 Mton) de worwd's second-wargest emitter of drainage-rewated peatwand CO2 (excw. extracted peat and fires). Totaw CO2 emissions from de worwdwide 500,000 km2 of degraded peatwand may exceed 2.0 Gtons (incwuding emissions from peat fires) which is awmost 6% of aww gwobaw carbon emissions.[54]

Peat has a high carbon content and can burn under wow moisture conditions. Once ignited by de presence of a heat source (e.g., a wiwdfire penetrating de subsurface), it smouwders. These smouwdering fires can burn undetected for very wong periods of time (monds, years, and even centuries) propagating in a creeping fashion drough de underground peat wayer.

Despite de damage dat de burning of raw peat can cause, bogs are naturawwy subject to wiwdfires and depend on de wiwdfires to keep woody competition from wowering de water tabwe and shading out many bog pwants. Severaw famiwies of pwants incwuding de carnivorous Sarracenia (trumpet pitcher), Dionaea (Venus fwytrap), Utricuwaria (bwadderworts) and non-carnivorous pwants such as de sandhiwws wiwy, toodache grass and many species of orchid are now dreatened and in some cases endangered from de combined forces of human drainage, negwigence, and absence of fire.[55][56][57]

It is estimated dat in 1997, peat and forest fires in Indonesia reweased between 0.81 and 2.57 Gt of carbon; eqwivawent to 13–40 percent of de amount reweased by gwobaw fossiw fuew burning, and greater dan de carbon uptake of de worwd's biosphere. These fires may be responsibwe for de acceweration in de increase in carbon dioxide wevews since 1998.[60][61] More dan 100 peat fires in Kawimantan and East Sumatra have continued to burn since 1997; each year, dese peat fires ignite new forest fires above de ground.

In Norf America, peat fires can occur during severe droughts droughout deir occurrence, from boreaw forests in Canada to swamps and fens in de subtropicaw soudern Fworida Evergwades.[62] Once a fire has burnt drough de area, howwows in de peat are burnt out, and hummocks are desiccated but can contribute to Sphagnum recowonization, uh-hah-hah-hah.[63]

In de summer of 2010, an unusuawwy high heat wave of up to 40 °C (104 °F) ignited warge deposits of peat in Centraw Russia, burning dousands of houses and covering de capitaw of Moscow wif a toxic smoke bwanket. The situation remained criticaw untiw de end of August 2010.[64][65]

In June 2002, de United Nations Devewopment Programme waunched de Wetwands Ecosystem and Tropicaw Peat Swamp Forest Rehabiwitation Project. This project was targeted to wast for 5 years, and brings togeder de efforts of various non-government organisations.

In November 2002, de Internationaw Peatwand (formerwy Peat) Society (IPS) and de Internationaw Mire Conservation Group (IMCG) pubwished guidewines on de "Wise Use of Mires and Peatwands – Backgrounds and Principwes incwuding a framework for decision-making". The aim of dis pubwication is to devewop mechanisms dat can bawance de confwicting demands on de gwobaw peatwand heritage, to ensure its wise use to meet de needs of humankind.

In June 2008, de IPS pubwished de book Peatwands and Cwimate Change, summarising de currentwy avaiwabwe knowwedge on de topic. In 2010, IPS presented a "Strategy for Responsibwe Peatwand Management", which can be appwied worwdwide for decision-making.